U.S. patent number 4,767,178 [Application Number 06/849,746] was granted by the patent office on 1988-08-30 for optical fiber connector having structure for ensuring predetermined spacing of optical elements.
This patent grant is currently assigned to Alps Electric Co., Ltd.. Invention is credited to Yoshinori Miyahara, Hiroaki Sasaki.
United States Patent |
4,767,178 |
Sasaki , et al. |
August 30, 1988 |
Optical fiber connector having structure for ensuring predetermined
spacing of optical elements
Abstract
A gap between end surfaces of optical converters provided at the
ends of optical guide paths of optical fibers is maintained with a
high accuracy and thereby optical coupling efficiency of such
optical converters can be improved with an optical fiber connector
comprising a plug engaging member at the end of optical guide path
and a plug which is removably engaged with said plug engaging
member having the structure that a spacer is provided between both
surfaces of said optical guide path ends, an optical guide path
hole is formed to said spacer and a constant gap is formed both end
surfaces of optical converters provided at the surface of said
optical guide path ends through said optical guide path hole.
Inventors: |
Sasaki; Hiroaki (Furukawa,
JP), Miyahara; Yoshinori (Furukawa, JP) |
Assignee: |
Alps Electric Co., Ltd.
(JP)
|
Family
ID: |
12911782 |
Appl.
No.: |
06/849,746 |
Filed: |
April 9, 1986 |
Foreign Application Priority Data
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|
|
|
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Apr 9, 1985 [JP] |
|
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60-52330[U] |
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Current U.S.
Class: |
385/88; 385/72;
385/73; 385/93 |
Current CPC
Class: |
G02B
6/3825 (20130101); G02B 6/4292 (20130101); G02B
6/3857 (20130101); G02B 6/3847 (20130101); G02B
6/3855 (20130101); G02B 6/3894 (20130101); G02B
6/3893 (20130101) |
Current International
Class: |
G02B
6/38 (20060101); G02B 6/42 (20060101); G02B
006/36 () |
Field of
Search: |
;350/96.20,96.21,96.22 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Balliet, L. & Sassen, B., "Optical Fiber End Separation Spacer
for Fiber Connectors", IBM Technical Disclosure Bulletin, vol. 27,
No. 4B, 9-1984, pp. 2427-2428. .
Wittmann, J. E., "Fiber Optics Interconnection System for Airborne
Electronics", 10th Annual Connector Symposium Proceedings, Oct.
19-20, 1977, pp. 212-224..
|
Primary Examiner: Lee; John
Attorney, Agent or Firm: Shoup; Guy W.
Claims
What is claimed is:
1. An optical fiber connector comprising:
a holding member having a front part for holding an end of an
optical fiber therein and a collar part extending radially outward
from the optical fiber, wherein a selected length is provided
between a front end surface of said front part and said collar
part;
a plug in which said holding member is disposed having an internal
part extending radially inward toward the optical fiber which abuts
against said collar part of said holding member to press it axially
in an insertion direction, and an engaging part formed integrally
with said internal part disposed toward a front end of said
plug;
a plug engaging member having a receptacle portion in which an
optical element is mounted, a front portion for receiving said
front part of said holding member, wherein said front end surface
of said holding member is to be disposed opposite the optical
element in said plug engaging member by a predetermined distance,
and an engaged part formed on said front portion which is removably
engaged with said engaging part of said plug;
a spacer having a thickness corresponding to said predetermined
distance and an optical path hole for light transmission
therethrough and being interposed in abutting contact between said
front end surface of said holding member and said optical element
when said front part of said holding member is inserted in said
front portion of said plug engaging member with said internal part
of said plug abuttingly pressing said collar part of said holding
member by a force of said engaging part of said plug engaged with
said engaged part of said plug engaging member;
wherein said length of said holding member is selected such that
when said holding member is inserted in said front portion of said
plug engaging member to bring said front end surface of said front
part of said holding member into abutting contact with said spacer,
a gap is provided between said collar part of said holding member
and said front portion of said plug engaging member which allows
sufficient space in case of differences in tolerances of said parts
such that said front portion of said plug engaging member does not
abut against said collar part, in order to ensure that said front
end surface of said holding member can be tightly pressed against
said spacer by the force of engagement of said engaging part of
said plug with said engaged part of said plug engaging member,
whereby the optical fiber end is accurately spaced opposite the
optical element by the thickness of said spacer.
2. An optical fiber connector as claimed in claim 1, wherein said
engaging part is an internal thread at the front end of an internal
cylindrical bore of said plug in which said holding member is
disposed, and said engaged part is a corresponding external thread
on said front portion of said plug engaging member.
3. An optical fiber connector as claimed in claim 1, wherein said
engaging part is a snap-in piece extending from the front end of
said plug and said engaged part is a corresponding step on said
front portion of said plug engaging member.
4. An optical fiber connector as claimed in claim 1, for forming an
optical connection between two optical fiber ends, further
comprising a second holding member for holding a second optical
fiber end disposed in a second plug, said second holding member
having a front part and a collar part, and said second plug having
an internal part, front end, and an engaging part, which parts are
the same as those of the first-mentioned holding member and plug,
wherein said plug engaging member includes a rear portion for
receiving the front part of said second holding member, the front
end surface of said second holding member constituting the optical
element in said plug engaging member which is to be disposed
opposite the front end surface of the first holding member by said
predetermined distance, and a second engaged part formed on said
rear portion which is removably engaged with the engaging part of
said second plug.
5. An optical fiber connector as claimed in claim 4, wherein the
length of said second holding member is selected such that when the
second holding member is fully inserted in the front portion of
said plug engaging member to bring the front end surface of the
front part of said second holding member into abutting contact with
said spacer, a second gap is provided between the collar part and
the rear portion of said plug engaging member, in order to ensure
that the front end surface of said second holding member can be
pressed against said spacer by a force of engagement of the
engaging part of said second plug with the second engaged part of
said plug engaging member, whereby the second optical fiber end is
accurately spaced opposite the first optical fiber end by the
thickness of said spacer.
6. An optical fiber connector as claimed in claim 4, wherein said
spacer is mounted in position in the center of said receptacle
portion of said plug engaging member between said front and rear
portions thereof.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a optical fiber connector for
removably coupling an optical converter at the end surface of
optical guide path provided for optical coupling between an optical
fiber and an optical conversion element such as LED,
phototransistor, photodiode, etc. and between optical fiber cables
and more specifically to a connector which can stabilize the
coupling efficiency by maintaining the coupling gap between
materials to be coupled with a high accuracy.
2. Description of the Prior Art
An optical data transmission system utilizing optical fibers and
optical conversion elements is now widely introduced into the field
of communication systems and particularly the optical fibers are
much expected for the future as a means of low loss and large
capacity data transmission line.
An optical data transmission system is required to use connectors
for coupling optical fiber and optical conversion element or end
surfaces of optical guide paths of optical fibers.
For the coupling of them, a constant gap (for example, about 50
.mu.m) must be prepared between end surfaces of optical converters
provided at the end part of optical guide paths.
Here, a prior art for coupling the optical guide paths of an
optical conversion element and an optical fiber is explained with
respect to FIG. 11 and FIG. 12. A light receptacle 1 comprises an
optical conversion element 2 such as a LED, phototransistor,
photodiode, etc. and is also provided with a cylindrical part 1b
having the external thread 1a. At the center of junction end
surface of such optical conversion element 2 is provided with an
optical converter 2a which is a light receptor and emitter
(consisting of receptor and emitter) and an elastic member 2b is
also provided at the rear surface of optical conversion element
2.
Meanwhile, a plug to be coupled with a light receptacle 1 is
composed of a holding member which holds an optical fiber 4 and a
cap nut having an engaging part 6a at the internal circumference
thereof. This holding member 5 continuously forms a front
cylindrical part 5a, a collar part 5b and a rear cylindrical part
5c. The front cylindrical part 5a holds an optical fiber 4, and
both end surfaces of front cylindrical part 5a and optical fiber 4
are ground to the same surface level. The rear cylindrical part 5c
holds an optical fiber cable 7 covering an optical fiber 4 and the
optical fiber cable 7 is fixed in such a fashion that a fixing
device 8 is engaged with the rear cylindrical part 5c which is also
formed with a slit 5d.
The plug 3 can be coupled with such light receptacle 1 in this way.
Namely, the front cylindrical part 5a of holding member 5 is
inserted into a cylindrical part 1b and the cap nut 6 is engaged
and both end surfaces of collar part 5b engages with the
cylindrical part 1b and the engaging part 6a of cap nut 6. In this
timing, the receptacle and plug are couplied in the condition shown
in FIG. 12, forming a gap A between the optical fiber end surface
and optical converter.
However, according to the prior art, the gap A between the optical
converter 2a of optical conversion element 2 and the end surface of
optical guide path of optical fiber 4 is determined by the length D
of the front cylindrical part 5a of holding member and positional
relation between the position where the collar part 5b collides
with the end surface of cylindrical part 1b of light receptacle 1
and the optical converter 2a of optical conversion element 2.
Therefore, the gap A includes fluctuation of the length B from the
internal rear wall 1c of light receptacle 1 to the cylindrical part
1b, the length C from the elastic member 2b provided at the rear
surface of optical conversion element 2 to the end surface of
optical fiber 4 And the length D from the end surface of holding
member 5 to the collar part 5b, and the gap A exceeds the desired
allowance of size and can no longer maintain the constant size. The
end surfaces of optical guide paths of optical converter 2a and
optical fiber 4 are, as a result, in contact with each other or
separated too much.
As described above, when the optical converter 2a and optical fiber
4 are in contact with each other, flaws may be generated at the
contact surface or dewing phenomenon is generated by water,
remarkably making unstable the optical signal transmission
characteristic. Moreover, if the gap A is too large, the conversion
efficiency in the optical signal transmission characteristic of
receptacle and plug is lowered and transmission intensity of
optical signal is deteriorated.
SUMMARY OF THE INVENTION
In order to accomplish the above-described objects, the
constitution of the present invention for an optical fiber
connector comprises: a holding member (16, 21b) holding the end of
an optical fiber and being abuttingly disposed in a plug (14, 21);
a plug engaging member (11, 23, 22a) removably engaged with the
plug and having a portion for receiving the end of the optical
fiber holding member therein; an optical element (12) disposed
within the plug engaging member which is to be located opposite the
optical fiber end by a predetermined distance; a spacer (13, 20,
24, 30) having a thickness corresponding to the predetermined
distance and having an optical path hole (13b, 20b, 24b, 30b) for
light transmission therethrough; an engaging portion (17b, 21c) of
the plug which is engaged with an engaged portion (11a, 23a, 22b)
of the plug engaging member so as to secure the plug and plug
engaging member together with the optical fiber holding member end
surface (16e, 17e, 21g) abutted against the spacer; and the holding
member having a length from its end surface to a collar portion
(16b), which is abuttingly pushed by a part (17a) of the plug, such
that a gap (B') is provided between the collar portion and the
receiving portion of the plug engaging member, in order to ensure
that the holding member end surface is abutted against the spacer
when the plug is engaged with the plug engaging member, whereby the
optical fiber end is accurately spaced from the optical element by
the spacer's thickness.
In brief and in accordance with one aspect of the prevent
invention, an optical fiber connector comprising an plug engaging
member at the end of optical guide path and a plug which is
removably engaged with said plug engaging member provides, in view
of attaining such object, the structure that a spacer is provided
between both surfaces of said optical guide path ends, an optical
guide path hole is formed to said spacer and a constant gap is
formed both end surfaces of optical converters provided at the
surface of said optical guide path ends through said optical guide
path hole.
In case of coupling optical conversion element and optical fiber or
optical fibers, the optical guide path supporting end surfaces of
optical fibers, etc. collide through the spacer and a optical guide
path hole is formed to such spacer. Therefore, a constant gap can
be provided between the end surface of optical converters provided
at the optical guide path end.
In this case, fluctuation of such gap is only the allowance of size
of thickness at the surface where the spacer exists and is not
related to fluctuation of other members. Thereby, a highly accurate
gap can be maintained and the coupling efficiency of optical
converters can be as much stabilized.
The novel features which are believed to be characteristic of the
invention, both as to organization and method of operation,
together with further objects and advantages thereof, will be
understood from the following description considered in connection
with the accompanying drawings in which several preferred
embodiments of the invention are illustrated by way of example. It
is to be understood, however, that the drawings are for the purpose
of illustration and description only and are not intended as a
definition of the limits of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 to FIG. 10 are embodiments of an optical fiber connector to
which the present invention is applied.
FIG. 1 is a sectional view illustrating the condition where an
optical fiber and an optical conversion element are to be
coupled.
FIG. 2 is a sectional view illustrating the coupling condition of
an optical fiber and an optical conversion element.
FIG. 3 is a perspective view illustrating separated condition of a
light receptacle.
FIG. 4 and FIG. 5 are sectional views illustrating other embodiment
of coupling condition of an optical fiber and an optical conversion
element.
FIG. 6 is a perspective view illustrating separated condition of a
light receptacle.
FIG. 7 is a perspective view illustrating separated condition of a
plug.
FIGS. 8 and 8(a) illustrate sectional views showing the before and
after conditions in which a snap-in type optical fiber and an
optical converter element are coupled to each other.
FIG. 9 and FIG. 10 are sectional views illustrating examples of
connector which couples optical fibers with each other.
FIG. 11 and FIG. 12 are sectional views illustrating a prior
art.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 to FIG. 10 illustrate embodiments of an optical fiber
connector in which the present invention is applied.
FIG. 1 to FIG. 7 represent respective examples of coupling an
optical conversion element and an optical fiber. Turning first to
FIG. 1, a light receptacle 11 (plug engaging member) comprises an
optical conversion element 12, for example, such as an LED,
phototransistor and photodiode, etc., a front part of the optical
receptacle 11 is provided with a cylindrical part 11b having
external threads 11a which is the engaged part of the connection.
Moreover, an optical converter 12a which is a light receptor/light
emitter (i.e. a light emitting or receiving element which forms one
side of the optical connection) is provided at the center of the
engaging surface 12b provided at the front side of optical
conversion element 12. Moreover, an elastic member 12d is provided
at the rear surface of the optical conversion element 12 and this
elastic member 12d is fixed with a fixing device 11c, and an
external lead 12e is provided to the optical conversion element
12.
Numeral 13 represents a spacer which has adequate thickness (about
50 .mu.m) and forms an optical guide path hole 13b. The external
circumference at the one side of this spacer 13 collides with the
front inner wall 11d of the light receptacle 11 and the other side
thereof collides with the engaging surface 12b of the optical
conversion element 12.
Meanwhile, a plug 14 which is coupled with the light receptacle 11
is composed of a holding member 16 which holds an optical fiber 15
and constituted by a cap nut 17 having an internal thread 17a which
is the engaging part of the connection that is threaded on the
external thread of the cylindrical part 11b so as to push the
collar part 16b in the plug insertion direction by abutment
therewith.
This holding member 16 is composed of a front cylindrical part 16a,
a collar part 16b and a rear cylindrical part 16c. The front
cylindrical part 16a holds an optical fiber 15. The front
cylindrical part 16a and the end surface of the optical fiber 15
are ground flush with each other to form the fiber end surface 15a
and holding member end surface 16e.
In FIG. 2, the end surface of holding member 16 collides with the
one side of spacer 13 and thereby the optical converter 15a of
optical fiber 15 is opposed against the optical converter 12a of
optical conversion element 12 through the optical guide path 13b of
spacer 13, holding a gap A' between such optical converters.
An optical fiber cable 18 having the covarage 18a at the external
circumference of optical fiber 15 is held by the rear cylindrical
part 16c and the optical fiber cable 18 is fixed by engaging a
fixing device 19 with the rear cylindrical part 16c forming a slit
16d.
The gap B' is formed between the end surface of cylindrical part
11b of light receptacle 11 and the end surface of collar part 16b
when the light receptacle 11 and plug 14 are coupled.
The length of gap B' is capable of absorbing all fluctuations in
the respective lengths E from the rear internal wall 11e to the ens
surface of cylindrical part 11b of light receptacle 11, C' from the
rear surface of elastic member 12d loaded to the optical conversion
element 12 to the engaging surface 12b of optical conversion
element 12 and D' from the front end surface of holding member 16
to the engaging surface of collar part 16b when it is set larger
than the fluctuation adding respective fluctuations of said
lengths.
Operations of this embodiment mentioned above will then be
explained hereunder.
When the front cylinder part 16a of the holding member 16 which is
holding an optical fiber 15 is inserted into the cylindrical part
11b of the light receptacle 11 and the cap nut 17 is engaged by the
thread with the external thread 11a of the light receptacle 11, the
holding member 16 enters the interior of light receptacle 11 while
the engaging part 17a of cap nut 17 is engaging with the collar
part 16b and the end part of holding member 16 is inserted up to
the position where it collides with the front end 12b of the
optical conversion element 12.
In this case, the other end of spacer 13 collides with the engaging
surface 12b of the optical conversion element 12 and thereby a
required gap A' is defined between the optical converter 15a of
optical fiber 12 and the optical converter 12a of optical
conversion element 12. Therefore, there is only a fluctuation of
gap A' and a gap having a high accuracy can be formed. Moreover,
fluctuations of other members are all absorbed by the gap B' and
the gap A' is not influenced by such fluctuations and an extra
external force is not applied to the optical converter 12a of
optical conversion element 12 by the front end of holding member
16.
FIG. 4 illustrates another embodiment of the present invention. The
same parts as those described above are given the same symbols and
these are not explained detail hereunder.
In FIG. 4, the front surface of optical conversion element 12 is
formed like a semi-circle, an engaging surface 12b is formed at the
base part, an elastic member 11d is loaded to the rear surface of
optical conversion element 12 and a fixing device 11e is also
provided.
20 is a cylindrical spacer of which one side forms the engaging
part 20a which engages with the engaging surface 12b of the optical
conversion element 12, while the other side forms the optical guide
path hole 20b and this spacer is loaded to the front internal wall
11f of the light receptacle 11. The end part of holding member 16
collides with the one side of spacer 20 and the gap A' between the
optical converter 15a of optical fiber 15 and the optical converter
12a is formed to about 50 .mu.m with a high accuracy. This gap A'
is not influenced by fluctuations of other members and includes
only fluctuation of the gap A' itself.
Of course the gap B' is set larger than a total sum of fluctuations
in the lengths C', D', E and the length F from the engaging surface
12b of optical conversion element 12 to the front internal wall 11c
of the light receptacle 11 and the gap B' absorbes such
fluctuations.
FIGS. 8 and 8(a) illustrate an example in which the connector parts
can be removably engaged with a snap-in type system, and the same
elements therein as that of the above-described embodiments are
referenced with the same characters.
A plug 21 of the snap-in type is connected and fixed to an engaging
cylindrical step 22a arranged at the front end of an optical
receptacle 22 (plug engaging member) by a plurality of split-type
engaging pieces 21a at the front end of the plug 21. The engaging
pieces 21a have inner circumferential step portions 21c which are
engaged with corresponding step portions 22b. The end surface 21g
of the holding member 21b holding the optical fiber end 15a is
thereby brought into abutting contact against the spacer 30 by the
engaging force of the engaging pieces 21a snapped onto the step
portions 22b.
Moreover, illustrated is an example where the spacer 30 having the
optical guide path hole 30b is provided between the optical
converter 15a at the optical guide path end of the optical fiber 15
and the optical converter 12a of the optical conversion element 12.
In the same figure, 21d a cylindrical part having the slit 21e
provided at the rear part of plug 21 and 21f is a fixing
device.
In the inserted condition shown in FIG. 8, a gap B' is provided in
the same manner as that of the above-described embodiments.
Each embodiment described above is an example of connector for
removably coupling optical converters at the optical guide path
ends of optical conversion element and optical fiber. The present
invention is not limited only to these embodiments. For example,
the present invention can also be adopted to the connectors which
removably couple the optical converters of optical guide path ends
of optical fibers as shown in FIG. 9 and FIG. 10.
In the same figures, the same parts as those in above embodiments
are given the same symbols. Numeral 23 represents an adapter (plug
engaging member) having external thread 23a for engaging the
optical converter 15a of optical fiber 15. The spacer 24 having the
optical guide path hole 24b is loaded to the center of this
adapter. The holding member 16 is inserted from both ends 23a, 23a
of the adapter 23 and the spacer 24 is provided between the holding
member 16, 16. As shown in FIG. 10, when the optical fibers 15, 15
are collided with each other, a cnstant gap A' is defined between
the end surfaces of optical converters 15, 15. As in the case of
above example, fluctuations of other members are absorbed by
providing the gap B'. Therefore, the gap B' allows space to be
present between the plug engaging member and the collar portion so
that they do not abut each other, even despite differences in
tolerances and dimensions of the various elements, whereby the end
surface of the holding member is always assured to be pushed
against the spacer. The plug 14 can select as required the
connecting means such as the snap-in system in addition to the
thread system illustrated in the figure.
As is obvious from above description, the present invention is
characterized by the structure that the plug engaging member at the
optical guide path end and plug are removably engaged with each
other. The spacer is directly abutted by the end surface of the
holding member which has a length that provides a gap B' so that
the engaging part can be engaged with the engaged part to press the
holding member against the spacer when the plug is inserted. The
spacer is provided between both surfaces of optical guide path ends
and a constant gap is defined between the end surfaces of the
optical converters through the optical guide path hole formed at
this spacer. Therefore, this gap A' includes only the fuctuation of
the gap A' itself and is not influenced by fluctuations of other
members. The gap A' can be defined with a high accuracy and is kept
constant even after the use for a long period of time, resulting in
a highly reliable connector. Moreover, the optical coupling
efficiency between the optical conversion element and optical fiber
and between the optical fibers can be much more stabilized.
Although particular embodiments of the present invention have been
described and illustrated herein, it is recognized that
modification and equivalents may readily occur to those skilled in
the art. Consequently, it is intended that the claims may be
interpreted to cover such modifications and equivalents and that
the invention be limited only thereby.
* * * * *